Dexter's ringing phone wakes him up. It's Dr. Vogel, who thanks Dexter for not killing Zach Hamilton. Deb calls and finds that Dexter woke up on the other side of town. Dexter thinks it's just a warning that Hannah drugged Dexter and Deb but didn't kill them. Dexter and Deb can't go to the cops because Hannah knows too much about them. Deb began to lose herself when she asked Dexter to kill Hannah. She's just starting to get back to normal and now Hannah is back. Deb doesn't want to deal with the situation and Dexter promises to take care of it.
While Dexter works from home, Zach shows up to ask why Dexter missed their meeting. Dexter tells Zach to never show up at his house and to never be seen in public together. He then says that Zach needs to get a job or some kind of cover life so that he looks ordinary. Finally, Dexter promises to help Zach with what he is going through.
At Deb's workplace, she gets upset at her boss, Jacob Elway, for being nosy and flirting with her. Elway tells her to show more gratitude, pointing out that he hired her when she was going through a very rough emotional time.
Dexter finds a traffic light picture of Hannah in a truck and writes down the license plate information. Using a fake voice, Dexter calls the rental place where the van was rented from. The rental place gives him the name and number of the person who rented out the truck. Dexter tells a vision of his father that Hannah wants to destroy Dexter and Deb's lives. His father says that Dexter should be scared of Hannah.
At the police station, Jamie brings up the topic of moving in with Quinn. He only wants to do so if their relationship keeps advancing, although he is in no rush to move in together. In another room, Vince's daughter, Niki, apologizes for blowing up at him. He was attempting to help Niki out but she thought the check was just to get her out of his life. They agree to meet for dinner.
Dexter finds Hannah on a boat down at the marina and follows her as she leaves. She enters a fancy restaurant but he isn't allowed in because of the dress code. He calls Zach and asks him to help Dexter get into the restaurant. Dexter and Zach split up to follow Hannah and the man she is with. Dexter confronts Hannah, who it turns out is out to dinner with her husband. She warns Dexter that her husband shouldn't see them together and that she changed her name to Maggie. Her husband, Miles, says he has heard how Dexter betrayed Hannah to the police. They leave the restaurant together. Zach asks Dexter why he didn't leave but Dexter takes full blame for what happened. When Zach asks if Dexter will kill Miles, Dexter says that he only kills people who deserve it.
While researching Miles, Dexter discovers that Miles is rich and powerful enough that he must have changed Hannah's identity for her. Deb visits Dexter's house: she reports that she can't find any information on Hannah. Dexter tells Deb about the meeting he had with her last night. Deb comes to the conclusion that Dexter is still in love with Hannah but Dexter denies it. She warns him that his feelings for Hannah will lead them to danger.
Vince pays a surprise visit to Niki, at the sports bar where she works. He is uncomfortable that it's a topless sports bar. She makes good money and enjoys her job but Vince is still wary.
Deb meets with Dr. Vogel and tells her how she is worried about Dexter and Hannah. Deb is unsettled that Hannah could kill them at any moment. Vogel warns Deb to consider all the possible complications before Deb takes matters into her own hands.
Zach shows up at the police station with his lawyer, who requests that Zach stop being monitored 24/7 by Quinn. Angel orders him to let the case go: there's no evidence that Zach committed any crime. In the next room, Vince tries to convince Dexter to hire someone part-time. He's trying to get a job for his daughter so that she stops being a topless waitress. Dexter meets with Zach outside the station and Zach is excited to start their business now that he isn't being followed. The first thing Zach must learn is how to control his urge to kill. He must channel his urge and be careful.
While at a gas station buying gas, Miles drives up next to Dexter. Miles mentions Dexter's son and says he would rather see Hannah in prison than lose her. He threatens to ruin Dexter's life if he tries to get back with Hannah.
Dexter meets up with Hannah at a greenhouse. He worries that Miles is a threat to her, but he also needs to find out if Hannah is a threat to himself and Deb. Hannah married Miles because he was there when Dexter wasn't. When Hannah escaped her old life, she knew she could go to Miles and get a new life and money. Hannah wanted Dexter to kill Miles but she changed her mind after seeing Dexter unconscious. She didn't want to ruin her relationship with him by manipulating him into carrying out her wishes.
Deb enters her boss' office and asks to use the high-tech GPS machine. She warns Elway that he doesn't want to get involved with her, but all he wants is a chance to find out.
Later, Deb attaches the GPS machine to the bottom of Dexter's car. Cassie sees her and asks if she can help her. Deb says that Dexter had mentioned her and Cassie is surprised that she was even brought up. Even though Dexter never called back, Cassie still likes him. Deb warns Cassie, that Dexter is not a mystery she wants to solve.
Vince waits outside the sports bar for Niki. He offers her the job at Miami Metro, but she isn't interested because she makes more money being a waitress. Vince is taken aback when Niki accidentally calls him dad. He thinks it would be in both of their best interests if she took the job.
Dexter visits Vogel to discuss Zach. Zach is getting anxious and he will need to kill soon. Vogel warns that Zach is Dexter's responsibility and Dexter to take Zach serious.
While walking to his car, Dexter is glad to not have to worry about Hannah. He has enough on his plate with Zach. Three men suddenly ambush and beat Dexter to the ground. He blames the ambush on Miles, who must have seen Dexter with Hannah. If Miles would have Dexter beaten, he worries what Miles will do to Hannah.
In her office, Deb apologizes to Elway. She thanks him for hiring her and knows that she wouldn't be in good shape if it wasn't for him.
Zach repeatedly knocks on the door of Dexter's apartment. He yells for Dexter but there is no answer. Cassie offers to leave Dexter a message for him and Zach says "Fuck him."
On Miles' boat, Miles confronts Hannah about meeting Dexter at the greenhouse. She says there is nothing going on between them but Miles doesn't believe her and restrains her. He says she will never have to leave the boat again and forces himself upon her. At the same time, Dexter sneaks onto the boat. He walks into the bedroom to find that Hannah has killed Miles in self defense. Dexter offers to help Hannah dispose of the body.
After dumping the body into the river, Dexter and Hannah talk about their relationship together. Hannah doesn't enjoy killing people. Across the parking lot, Deb is watching the two of them. Dexter receives a text and must leave for a crime scene at his apartment building. He asks Hannah not to leave town before talking to him again.
At Dexter's apartment building, he finds Cassie's body in her apartment. The murder is similar to the style of the Norma Rivera killing. He wonders if Zach also killed Cassie. Dexter reflects that his teacher was a normal person and that led to Dexter being taught well. He worries about what will happen with two murderers working together.